If you are having an issue with Spectrum email not sending on Windows 10 email, it might be because of the configuration of Spectrum account on any third party. To resolve the issue, use proper settings:
Username: Your Spectrum email address.
Password: Spectrum email password.
Along with it, SSL should be on.
For protocol, set the field to IMAP.
Use mobile.character.net for the incoming mail server.
The incoming email server port number will be 993.
For outgoing mail servers, use mobile.character.net
And, the port number for the outgoing email server will be 587.
The last step is to tap on the yes option and choose the checkbox which is next to require authentication field.